I've bought a medical device (Giger MD), which collects data during the patient's exercise and send the data to a computer. An UTP cable connects the device to a 9-way D-SUB female, and that should be connected to the PC.

I've also bought the software CD, which is compatible with Win 95/98 OS.

I could successfully install the program on my laptop which has Windows 7, and have tested to connect the D-SUB via a D-SUB to USB adapter to the PC. However, the PC recognizes the device as a mouse.


  • What could be the main problem? The OS? The adapter?
  • Do you think an D-SUB to VGA adapter could be the solution? (Because I don't have one, but may purchase)
  • Is it totally hopeless to get these things running with this configuration? Should I find an older PC?

Let me know if further information is necessary.

  • 1
    I suggest contacting the manufacturer, as they will know what cables are needed etc. Their current product works with Windows 7 so they should also know how to get your device working. Commented Jul 7, 2023 at 15:40
  • 4
    Since presumably the device uses serial port protocols, your issue seems to be in the D-Sub to USB adapter-- either the hardware or the driver. "D-sub to USB" isn't really a spec, so it's hard to say what the problem is. Commented Jul 7, 2023 at 18:21
  • 5
    Turn off PNP enumeration for the COM port, or plug in USB adapter first, then connect D9 cable.If Windows is set to detect for mice on new COM ports, and the device accidentally looks like a mouse, then Windows thinks it must be a mouse.
    – Justme
    Commented Jul 8, 2023 at 7:19
  • 13
    Why do you think connecting (something detected as) a mouse to a VGA port is a good idea? I am not able rightly to apprehend the kind of confusion of ideas that could provoke such a question. Commented Jul 8, 2023 at 8:20
  • 3
    Do NOT connect random equipment to VGA/serial ports, just because it fits. You can end up blowing up the port (silently) without knowing that you have done it. Some old PCs and 25way sockets and plugs. One was for serial, one was for parallel. I've known of cables being connected to the wrong port, just because they fitted. When I came to diagnose the problem, it could no longer be fixed because something on the serial/parallel port circuit on the motherboard had been fried.
    – cup
    Commented Jul 12, 2023 at 10:42

2 Answers 2


2 rows 9 pins D-SUB 9 (or Cannon 9) connectors were used on PC for serial COM ports (RS232) and in even older days also for IIRC EGA/CGA monitor connection.

My bet is that it's the serial port (you can check with multimeter if GND is on the right place - IIRC pin 5). Serial port uses male Cannon 9 connector on the PC side and female connector on the cable (or device if plugged directly) which matches your description.

Nowadays machines do not usually have RS232 any more, so in such case you need a USB to RS232 or USB 2 COM port adapter first which might be a big problem on W9x with drivers for it and also the cheap ones might not work at all with your device... there were also ISA alternatives. Any decent IDE card had RS232, GAME and LPT on-board but again having ISA on modern machine is luxury (even PCI these days) unless you have a developer machine style motherboard (these are quite expensive but have "all" the old stuff onboard).

Now if you run W9x program on Win7 it means you have 32bit OS version (on x64 you can not run 16bit apps any more) which is fine but problem is W9x drivers are not compatible with win7. And also RS232 does not have any notion of VID/PID so you have to select/install correct driver manually. NEVER USE automatic driver install for it - Windows will almost always choose wrong driver.

If your device is old and discontinued and not very common you will have most likely no chance of getting win7 compatible driver (there are online driver writing services out there just for these cases, but it's not for free. IIRC it was called driverguide or something like that; formerly it was database of old drivers so if you are in luck it might contain what you need already).

So I would try some emulator or virtual machine similar to DOSBOX to run Win9x virtually inside your Win7 (beware that MS Virtual PC does not work on Win7 correctly; it was my favourite up to XP as it was really simple small and free, but after they ported it to Win7 it's unreliable and crashes a lot). There are quite few of them out there like WMware; just google it. After that run your app inside it with the old drivers installed there too. It should work normally as on real machine if the emulator supports COM port forwarding...

If all fails, you could try to reverse the communication protocol yourself as RS232 COM port serial communication is pretty easy (just file access - you do not even need a driver). However you would need some stuff about the device yourself (ideally capture the data between old machine and device during usage) and then either create your own app for using the device or somehow inject the data into the Win9x app (similar to what DOSprint does). However you never described what the device is ...

  • I think you're getting confused here about Win32. Both Windows 95 and Windows 7-x64 support the Win32 API, and that was in fact the native API for Win95. And you do need a COM port driver, even today. It's probably included with the RS-232 to USB adapter (good chance that's an FDTI-based product)
    – MSalters
    Commented Jul 14, 2023 at 7:03
  • @MSalters no confusion at all as its not about win32 API (the application runs) but drivers for the device. As win9x drivers are not usable on winXP,win2K,winNT and latter windows OS... Its similar like you would want use MS-DOS device driver on win9x ... Also what I meant by x64 version many old w9x apps where 16bit not 32bit and they do not run on 64bit OS as MS dropped the support for them.
    – Spektre
    Commented Jul 14, 2023 at 7:09

The fact that Windows thought it was a mouse is a really good sign, and likely means that things are nearly working properly.

First of all, there's no way that Windows would mistake a USB serial port device for a USB mouse. What's happening is, it's detecting the serial port (step one complete!) and automatically running its mouse detection routines. Those work by sending certain control signals and looking for a mouse-like response. Unfortunately, there were a number of serial mouse protocols, and a random non-mouse serial device will often unintentionally send data which will fool the mouse detection. But that means you're receiving serial data from the device (step two complete!).

So the only thing currently going wrong is the mouse driver squatting on your serial port. See this SO question for how to stop that from happening. With that resolved, the host program (which is successfully installed - step three complete!) should be able to configure the port and communicate, with no need for any additional drivers or OS-level configuration.

As others have mentioned, heedlessly plugging a random DE-9 into a no-name USB-serial bridge was a really bad idea. But you got lucky. Nevertheless: That connection is not hotplug-safe. Do not plug or unplug the serial cable while the computer OR the device is turned on or sleeping, or you may actually seriously break something (possibly your computer).

  • 1
    I've had Windows falsely regard serial ports as containing mice. It's a real nuisance, and strikes me as absurdly silly. While it might be useful to provide a means by which someone with a serial port mouse could configure their system to use it, the probability that a device which continuously outputs a stream of serial data may be misidentified as a mouse, with the effect that the device data is interpreted as a bunch of arbitrary mouse movements and mouse clicks! seems vastly greater than the probability of someone actually wanting to use a vintage mouse.
    – supercat
    Commented Jul 12, 2023 at 15:35
  • I also suspect that if someone did actually want to use a vintage mouse, a serial-mouse-to-HID converter could probably work slightly more smoothly than a serial-to-USB bridge with a mouse driver.
    – supercat
    Commented Jul 12, 2023 at 15:37
  • This answer is correct as it expands my comment into an answer. However there are wrong details. How is the connection unsafe for hotplug for example? I know there might be many reasons but you don't say even one. If it's unsafe to connect while computer is on or sleeping, it isn't any safer when computer is off either, if it is plugged to same mains plug and same external peripherals than when it is on.
    – Justme
    Commented Jul 12, 2023 at 21:43
  • @Justme For the normal reason: it may cause a potential between pins which don’t expect it. But the OP’s question was not about the electronic details of hot-plugging.
    – Sneftel
    Commented Jul 13, 2023 at 5:08
  • @Sneftel The potential difference will be as just unsafe regardless of the PC being turned on or off - it does not matter a bit. If there is a dangerous potential difference when PC is on, why would it go away simply by turning PC off?
    – Justme
    Commented Jul 13, 2023 at 5:19

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